1. Field of the Invention
The present invention generally relates to a seatbelt device seeking the safety of a passenger by securing such passenger to a vehicle seat with a webbing (seatbelt), and particularly relates to a seatbelt device capable of controlling the operation of the collision-safety mechanism by providing to a buckle a function of detecting the passenger sitting in a seat or the fastening of a webbing.
2. Description of the Related Art
As an example of a conventional passenger detector for detecting the passenger in a vehicle, there is Japanese Patent Laid-Open Publication No. Hei 2-31964. This invention is provided with a supersonic sensor on the inner side of the door, and detects the existence of a passenger by utilizing the supersonic signals emitted from the supersonic sensor and the supersonic signals entering the supersonic sensor upon being reflected by the passenger.
Further, the invention of Japanese Patent Laid-Open Publication No. Hei 9-20194 proposes a structure wherein a sensor for detecting the passenger is arranged on the upper face of the dashboard and uses the inclined windshield as the sensor wave reflector so as to avoid the complexity of the cable wiring of supersonic sensors provided on the inner side of doors, and to seek and secure excellent reliability.
Moreover, detection of the fastening of a webbing is vital in a seatbelt device, and, for example, is conducted with a buckle switch provided within the buckle that engages with a tongue plate. A buckle sensor used for detecting the fastening of such webbing is demanded of high reliability in order to protect the passenger.
Nevertheless, with conventional passenger sensors arranged inside doors and on dashboards, the distance from the sensor to the passenger or the principle emission direction of the sensor wave and the passenger position is displaced upon the passenger sliding one's seat or reclining the backrest. Thus, in order to accurately detect the passenger, parameters such as the scope (sensitivity, directivity) of sensor detection distance must be corrected in conformity with the displacement of such sliding or reclining.
In addition, conventional buckle sensors did not go as far as to confirm whether the buckle switch was operating normally. One reason for this was due to the diagnosis of a buckle switch malfunction requiring a complex structure that would enable the compulsorily closing or opening of the buckle switch. Thus, such structure would not fit inside the buckle, or would make the buckle excessively large.
Moreover, it would be costly if the passenger sensor and buckle sensor were to be installed separately.